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Anonymous Monk has asked for the
wisdom of the Perl Monks concerning the following question:
what is a regular expression to match a word containging all and only a set of characters?
egs:
for the set t,a,b
tab should match and bat should match but not bbat or brat!
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Re: regular xpression stuff
by Masem (Monsignor) on Jan 20, 2002 at 21:00 UTC
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In this case, you don't want a regex, at least directly. I think we've golfed this once, but in general:
my $to_be_matched = 'tab';
my $word = 'bat';
if ( join '', sort split(//, $word) eq
join '', sort split(//, $to_be_matched ) ) {
# Success!
} else {
# Failure
}
Update - $ instead of @ on to_be_matched
-----------------------------------------------------
Dr. Michael K. Neylon - mneylon-pm@masemware.com
||
"You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important
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[d/l] |
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if ( join '', sort split(//, $word) eq
join '', sort split(//, $to_be_matched ) ) {
be
if ( join('', sort split(//, $word)) eq join('', sort split(//, $to_be
+_matched)) ) {
(extra parenthesis added )
After adding the parenthesis , i get "Success" (i.e. "bat" = "tab" based on your example), without them the result is "Failure"
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[d/l]
[select] |
Re: regular xpression stuff
by Parham (Friar) on Jan 20, 2002 at 21:24 UTC
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$var = 'bat';
if ($var =~ /^[bat]{3}$/) { print "match"; } else { print "fail"; }
since you want only those letters to exist, check from beginning to end that word for each letter, the {3} should be the number of letters in that word | [reply]
[d/l] |
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If I'm understanding the question correctly, this will not work.
It seems that the inquiring monk wants to match each letter once and only once.
/^[bat]{3}$/ could match 'ttt', 'bba', 'aaa', etc. If that *is* undesirable, Masem's excellent reply is probably the best way to go.
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[d/l] |
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count0++ i forgot to take that into consideration
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Re: regular xpression stuff
by Lucky (Scribe) on Jan 20, 2002 at 22:01 UTC
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Looks terrific but works:
@to_check=('bat','bbat','brat');
for (@to_check){
if (/^([bat])(?!\1)([bat])(?!\2)([bat])(?!\3)/){
# do something
}
}
Just create regexp dynamically.
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[d/l] |
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if (/^([bat])(?!\1)([bat])(?!\2)([bat])(?!\3)/){</i>
This does not entirely work, 'bab', for instance, passes the match.
the following modified version works, but it is not too elegant, just imagine checking a 5 letter word!
if (/^([bat])(?!\1)([bat])(?!\2|\1)([bat])(?!\3|\2|\1)/){
Will perl for money
JJ Knitis
(901) 756-7693
gt8073a@industrialmusic.com | [reply]
[d/l]
[select] |
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my $set='bat';
my $regexp;
for (my $i=1;$i<=length($set);$i++){
my $x=join '|', map {"\\$_"} 1..$i;
$regexp.="([$set])(?!$x)";
}
if (/^$regexp/){
# do something
}
Terrible... :-) | [reply]
[d/l] |
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